What battery life should I expect on iOS when using ergdata?

[gcanyon]

I started a marathon with 95% battery on an iPhone 5s, and was down to 40% battery left with 25k still to go on the marathon. I'm slow, but I'm not that slow.

I was using a polar heart rate monitor, which probably eats some battery on its own.

[lcantey]

I don't use ErgData but do use a heart rate monitor and an app like RunKeeper or iSmoothRun it *definitely* eats into the battery life. On a marathon I knew it could be close and have it on power to avoid the issue. For half marathons I don't bother but will try to top it off later.

[gcanyon]

It looks like it was a fluke. I've since done a half marathon and the phone only lost about 20% in that time. So assuming nothing goes wrong, I should be able to easily row a marathon with the heart rate monitor and ergdata.

[Drivetofast]

I tried to see how long my iPhone 5s would last. I was able to row 5 1/2 hours before it went out. So I don't see a Problem for a full marathon. I will try again at later date or next month

[gcanyon]

I just completed a marathon in roughly 3:30 and had about 45% left when done. So whatever was going on the day I posted my original results, it seems it wasn't ergdata's fault.